The advantages of using polarization selective surfaces for linear polarization have been known for quite some time and have been used in squirrel cage antennae, polarization twist antennae and cassegrainian antennae. For example, polarization selective surfaces have been successfully used to eliminate aperture blockage in cassegrainian antenna systems in which a subreflector is formed of parallel, closely spaced (with respect to wavelength) wire. Such a surface is completely reflective for polarization parallel to the grid and nearly transparent for perpendicular radiation.
Thus, incident radiation which is polarized parallel to the grid is completely reflected onto the main dish of the antenna. The main dish is arranged to rotate the incident polarization by 90.degree.. The rotated and reflected radiation, being perpendicular to the subreflector, will pass through unhindered, thus eliminating aperture blockage. Heretofore, the use of polarization selective surfaces have been confined to linear polarization and has not been extended to circular polarization because of the lack of a surface which is sensitive to the vertical and horizontal components of circular polarization.